/*
 ============================================================================
 Page	     : 295
 Name        : ptr_ops.c
 Date	     : 20210405
 Author      : Hbue 18060333
 Copyright   : Your copyright notice
 Description : 指针操作
 ============================================================================
 */

#include <stdio.h>

int main(void)
{
	int urn[5] = { 100, 200, 300, 400, 500 };
	int *ptr1 = NULL;
	int *ptr2 = NULL;
	int *ptr3 = NULL;

	ptr1 = urn;				// 把一个地址赋给指针
	ptr2 = &urn[2];				// 把一个地址赋给指针
						// 解引用指针,以及获得指针的地址
	printf("pointer value, dereferenced pointer, pointer address:\n");
	printf("ptr1 = %p, *ptr1 = %d, &ptr1 = %p\n,", ptr1, *ptr1, &ptr1);

	// 指针加法
	ptr3 = ptr1 + 4;
	printf("\nadding an int to a pointer:\n");
	printf("ptr1 + 4 = %p, *(ptr1 + 4) = %d\n", ptr1 + 4, *(ptr1 + 4));
	ptr1++;					// 递增指针
	printf("\nvalues after ptr1++:\n");
	printf("ptr1 = %p, *ptr1 = %d, &ptr1 = %p\n", ptr1, *ptr1, &ptr1);
	ptr2--;					// 递减指针
	printf("\nvalues after --ptr2:\n");
	printf("ptr2 = %p, *ptr2 = %d, &ptr2 = %p\n", ptr2, *ptr2, &ptr2);
	--ptr1;					// 恢复为初始值
	++ptr2;					// 恢复为初始值
	printf("\nPointer reset to original values:\n");
	printf("ptr1 = %p, ptr2 = %p\n", ptr1, ptr2);
	// 一个指针减去另一个指针
	printf("\nsubtracting one pointer from another:\n");
	printf("ptr2 = %p, ptr1 = %p, ptr2 - ptr1 = %td\n", ptr2, ptr1, ptr2 - ptr1);
	// 一个指针减去一个整数
	printf("\nsubtracting an int from a pointer:\n");
	printf("ptr3 = %p, ptr3 - 2 = %p\n", ptr3, ptr3 - 2);

	return 0;
}

